Three-dimensional tumor model mimics stromal - breast cancer cells signaling

// Stephanie Lemmo Ham 1 , Pradip Shahi Thakuri 1 , Madison Plaster 1 , Jun Li 2 , Kathryn E. Luker 3 , Gary D. Luker 3 and Hossein Tavana 1 1 Department of Biomedical Engineering, The University of Akron, Akron, OH 44325, USA 2 Department of Mathematical Sciences, Kent State University, Kent, OH 44242, USA 3 Department of Radiology, Microbiology and Immunology, Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA Correspondence to: Hossein Tavana, email: tavana@uakron.edu Gary D. Luker, email: gluker@umich.edu Keywords: TNBC; tumor-stromal signaling; CXCL12; CXCR4; three-dimensional culture Received: August 09, 2017      Accepted: November 09, 2017      Published: December 05, 2017 ABSTRACT Tumor stroma is a major contributor to the biological aggressiveness of cancer cells. Cancer cells induce activation of normal fibroblasts to carcinoma-associated fibroblasts (CAFs), which promote survival, proliferation, metastasis, and drug resistance of cancer cells. A better understanding of these interactions could lead to new, targeted therapies for cancers with limited treatment options, such as triple negative breast cancer (TNBC). To overcome limitations of standard monolayer cell cultures and xenograft models that lack tumor complexity and/or human stroma, we have developed a high throughput tumor spheroid technology utilizing a polymeric aqueous two-phase system to conveniently model interactions of CAFs and TNBC cells and quantify effects on signaling and drug resistance of cancer cells. We focused on signaling by chemokine CXCL12, a hallmark molecule secreted by CAFs, and receptor CXCR4, a driver of tumor progression and metastasis in TNBC. Using three-dimensional stromal-TNBC cells cultures, we demonstrate that CXCL12 – CXCR4 signaling significantly increases growth of TNBC cells and drug resistance through activation of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) pathways. Despite resistance to standard chemotherapy, upregulation of MAPK and PI3K signaling sensitizes TNBC cells in co-culture spheroids to specific inhibitors of these kinase pathways. Furthermore, disrupting CXCL12 – CXCR4 signaling diminishes drug resistance of TNBC cells in co-culture spheroid models. This work illustrates the capability to identify mechanisms of drug resistance and overcome them using our engineered model of tumor-stromal interactions.